the 6502-based CPU board he’s put together is by far the most impressive. On his site Ben outlines his design process, and deep dives into how he got a 6502-based card to talk to a Z80-based system. This isn’t a trivial feat as the two processors have very different design philosophies—with the 6502 using a strict synchronous bus, and the Z80 using a loosely asynchronous bus. He then talks about software before doing some crude performance testing.